As a most widely used composite membrane variety, a polyamide composite membrane has a structure formed by forming a polyamide separation layer on a non-woven polysulfone fabric supporting layer through an interface polymerization reaction (the interface polymerization reaction refers to polycondensation performed on an interface or at an organic phase side of an interface of two solutions which do not dissolve each other and respectively dissolve two monomers) (such as U.S. Pat. No. 5,160,619, CN1724130A, etc.). The polyamide composite membrane has the advantages of high interception rate, high flux, excellent chemical stability, wide range of pH values (4 to 11), low requirement for operating pressure and the like. Water flux is one of most important performance parameters of the polyamide composite membrane. The higher the water flux is, the lower the energy consumption for treating different amounts of liquid is. Although an energy utilization rate of large-sized water treatment apparatuses is continuously increased at present, nearly half of the cost is still limited to the consumed electric power. From the point of view of increasing the production efficiency and reducing the equipment operating cost, it is crucial to control the cost by reducing the energy consumption.
A compactness degree of an active separation layer of the polyamide composite membrane decides the performance of the composite membrane. The more compact the active separation layer is, the larger the resistance to the water molecules is, and the higher the interception capacity to salt ions is. Conversely, the looser the active separation layer is, the smaller the resistance to the water molecules is, and the lower the interception rate to the salt ions. In order to increase the water flux of the polyamide composite membrane, the research personnel add different hydrophilic micromolecular additives into a water-phase reaction solution and an oil-phase reaction solution to promote the hydrolysis of poly-acyl chloride, thereby forming a loose active separation layer. For example, in U.S. Pat. Nos. 5,254,261 and 6,171,497, the water flux of the composite membrane is increased by adding amine salt and isopropanol into the polyamine aqueous solution. However, in the polyamide composite membrane, little addition amount of the traditional additives generates an unapparent effect on improving the membrane performance, while the large addition amount may influence the stability of the water-phase solution and the oil-phase solution, resulting in sharp reduction of the membrane performance.
Therefore, an invention of a polyamide composite membrane with high interception rate and high water yield is of great significance.